Very brief backstory:
My approximately 18 yr old gelding (Morgan/Standardbred, we think) started going lame about 5 years ago. I had a few vets look at him now and again, they all basically told me it was arthritis in his hocks, and to put him on supplements (since I was a poor college student and couldn't afford injections). He's been on and off lame since. He eventually became pretty much only sound at the walk, but fine in the pasture, still able to play around and keep up with his buddies. Within the past year he's gotten pretty bad. The vet came out at one point this winter, and we figured out he had Lyme Disease. We treated him, and he tested negative again. He gained his weight back, but he still is seriously lame at anything faster than a walk.
I'm leaving some stuff out, but basically he has been on every supplement known, and nothing has helped. My vet came to see him yesterday (I've been trying to get her out for a while), since I now have a steady income and can afford injections. Low and behold, she thinks it's his hips (possibly just the right one), not his hocks at all. So we are going to the clinic next Friday to get x-rays and see what she can do for him. He's a pasture ornament, and I'm prepared to pay for him until the day he dies, but I want him to be comfortable and healthy!
Anyway, this leads me to my real question. While she was examining him, she recommended Osteopathy. Apparently she recently got into it, and has an experienced vet that helps her, but thinks some manipulation might really help my guy out. She specifically identified the dip in front of his withers was due to a muscle pulling down in his shoulders, not the little crest and lack of general muscle I thought it was from. She said it's causing him to not stretch out all the way in the front, and that she could easily fix it. She doesn't know if it will help his hips at all, but she said it couldn't hurt.
TL;DR: Has anyone ever had any Osteopathy work done on their horses (or themselves!)? Does anyone know anything about it? I've watched all the youtube videos I can, and googled it, so I know the basic principles, but I'd like to get some first hand feedback on it. Did it help? How long did it take? My vet said I can expect it to be around 3 hours long! Is that normal, or is my old man just seriously screwed up?
Thanks in advance!
Pony in question (you can kinda see the thing with his neck, which is why I picked this picture):
(edited b/c I forgot a title!)